Associative learning is supported by the ability to recognize errors between expected and actual outcomes. Evidence from primate and rat recording studies suggests that dopaminergic neurons in substantia nigra and the ventral tegmental area (VTA) signal such prediction errors. However, generating such prediction errors presumably requires the comparison of actual outcomes to expected outcomes. Perhaps the best candidate for signaling such outcome expectancies is the orbitofrontal cortex (OFC). This proposal will test this hypothesis, using inactivation and single-unit recording to ask how OFC is involved learning and in the calculation of prediction errors in dopaminergic VTA neurons during Pavlovian blocking.